/* booksave.c -- saves structure contents in a file */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAXTITL 40
#define MAXAUTL 40
#define MAXBKS  10				/* maximum number of books */
char * s_gets(char * st, int n);
struct book {					/* set up book template	   */
	char title[MAXTITL];
	char author[MAXAUTL];
	float value;
};

int main(void)
{
	struct book library[MAXBKS]; /* array of structures    */
	int count = 0;
	int index, filecount;
	FILE * pbooks;
	int size = sizeof(struct book);

	if ((pbooks = fopen("book.dat", "a+b")) == NULL)
	{
		fputs("Can't open book.dat file\n", stderr);
		exit(1);
	}

	rewind(pbooks);				/* go to start of file    */
	while (count < MAXBKS && fread(&library[count], size,
		                           1, pbooks) == 1)
	{
		if (count == 0)
			puts("Current contents of book.dat:");
		printf("%s by %s: $%.2f\n", library[count].title,
			   library[count].author, library[count].value);
		count++;
	}
	filecount = count;
	if (count == MAXBKS)
	{
		fputs("The book.dat file is full.", stderr);
		exit(2);
	}
	puts("Please add new book titles.");
	puts("Press [enter] at the start of a line to stop.");
	while (count < MAXBKS && s_gets(library[count].title, MAXTITL) != NULL
		   && library[count].title[0] != '\0')
	{
		puts("Now enter the author.");
		s_gets(library[count].author, MAXAUTL);
		puts("Now enter the value.");
		scanf("%f", &library[count++].value);
		while (getchar() != '\n')
			continue;				 /* clear input line */
		if (count < MAXBKS)
			puts("Enter the next title.");
	}

	if (count > 0)
	{
		puts("Here is the list of your books:");
		for (index = 0; index < count; index++)
			printf("%s by %s: $%.2f\n", library[index].title, 
				   library[index].author, library[index].value);
		fwrite(&library[filecount], size, count - filecount,
			   pbooks);
	}
	else
		puts("No books? Too bad.\n");

	puts("Bye.\n");
	fclose(pbooks);

	return 0;
}

char * s_gets(char * st, int n)
{
	char * ret_val;
	char * find;
	ret_val = fgets(st, n, stdin);
	if (ret_val)
	{
		find = strchr(st, '\n');	// look for newline
		if (find)					// if the address is not NULL,
			*find = '\0';			// place a null character there
		else
			while (getchar() != '\n')
				continue;			// dispose of rest of line
	}
	return ret_val;
}